This research proposal makes use of the autoantibodies which occur in the sera of patients with systemic lupus erythematosys and other connective tissue diseases. Many of these autoantibodies are antinuclear antibodies. A number of these antinuclear antibodies have been demonstrated to react with nonhistone nuclear proteins which are ocidic in character. There are two main objectives in this research project. One of these is to employ the antinuclear antibodies as reagents to help isolate and characterize the nature of the homologous nonhistone protein antigens. In this way, more information concerning these nuclear proteins can be obtained. The second objective is to determine the clinical significance of these different antinuclear antibodies. Initial studies have demonstrated that some antibodies such as the antibody to a nuclear acidic protein called Sm antigen, is highly restricted to systemic lupus erythematosus. Antibodies to other acidic proteins may be more widely prevalent and may be present in many connective tissue diseases. With studies of this nature, clinical correlations of different antinuclear antibodies may be present in many connective tissue diseases. With studies of this nature, clinical correlations of different antinuclear antibodies may be obtained. BIBLIOGRAPHIC REFERENCES: Arroyave, C.M., M.R. Wilson and E.M. Tan. Serum factors activating the alternative complement pathway in autoimmune disease: Description of two different factors from patients with systemic lupus erythematosus. J. Immunol. 116:821-826, 1976. Kurata, N. and E.M. Tan. Identification of antibodies to nuclear acidic antigens by counterimmunoelectrophoresis. Arthritis & Rheumatism 19:574-580, 1976.